Apparatus for automatically printing two faces of an object



United States Patent 4 4000 00 22444 44 l HHUlHH M29 000200 7 1011.1 11 l 0". "HM w m a m mm mm" s n a .nu h wm vto mo uu a fl dmbb aaha su uu HHBKMURMDD 9013466667 5666666666 9999999999 1111111111 182 2557 6 11 1 5795028448 8126013524 J ,3 ,2 w 7819903963 6470555582 ,9 J pl w w w 2223333333 G. N I T N I. m e c Y n .L m L F A flw w M m m M e t 0 979 T er ht 191 U 83 2 A fl 6 R l c .w Zfl fl O u 0 h fl s F. 03. rs L66AOAF5 m T .l 0 d A m N mW R a mi A V Dfimm W n .l r l AFPP A U nflna s 4 7 224333 5 1 111111 1 Primary ExaminerRobert E. Pulfrey Assistant ExaminerClifford D. Crowder Attorney Spencer and Kaye TWO FACES OF AN OBJECT 5 Claims, 4 Drawing Figs.

ABSTRACT: A machine for printing two surfaces of an object of oval cross section comprises two printing stations at each of which a rotary device presents the object to a printing means in such a way that the surface to be printed rolls without sliding in contact with the printing device. The objects are trans- [56] References Cited UNITED STATES PATENTS 11/1957 ferred from one printing station to the other by means of a transfer fork carried at the end of a lever forming one side of a 101 /35UX parallel lever system such that movement of the fork is tangen- 4/1938 Simonton tial to the path oftravel ofa body in one ofthe rotary means.

Patented Qct. 13,, 1970 3,533,353

Sheet INVENTORZ Lauis Gilberfi Dubui'e Patented Oct. 13, 1970 3,533,353

Sheet Z of 4 ET mvEmon; LOU-i5 Gilbeu-l; Dubui BY mfmm &

INVENTOR'.

Louis Cuber: Dubai? BY &

A "LDl-HCYS Patented Oct. 13, 1970 Sheet 1 014 Inventor;

Lou ls Gilbert Dubuit 3 gg owwzi Aiouri,

APPARATUS FOR AUTOMATICALLY PRINTING TWO FACES OF AN OBJECT This invention relates to machines for the continuous print ing of two surfaces of an object with an oval transverse section and is directed more particularly to machines using the "silk screen" method of printing.

Such machines, and for example. those of the type described in applicant's US. Pat. No. 3.286.624 issued on Nov. 22, I966. generally comprising two printing stations and a transfer means established between the two printing stations for transferring one object from one station to the other. each printing station including a printing device and directly above or below this, a rotary device adapted to seize an object and to make it roll without slipping at contact with the printing device, while the said transfer means is adapted to move from a first position where it seizes an object carried by the rotary device associated with the first printing station. after printing one of the surfaces of the said object to a second position. where it places the said object on the rotary device associated with the second printing station for printing the other of the surfaces of the said object.

An object of the present invention is to provide various im provements to machines of this type. mainly intended to improve the working reliability of the machines and to increase the rate of the work.

In accordance with one aspect of the invention there are provided printing stations for performing silk screen printing. each station comprising a horizontally movable carriage, a silk screen and a scraper carried by the carriage and vertically movable relative to it, in combination with a rotary device formed by a base and a gripping tip movable in the direction of the base for urging an object to be printed toward the base. The base and the tip are synchronously rotated by the action of at least one toothed rack movable horizontally in unison with the screen. The alternating horizontal displacement of the carriage is ensured by a control means, which operates a rotary cam whose profile is made in such a way as to ensure a stopping time, determined with reference to the carriage, at each of the extreme positions of the horizontal displacement.

The gripping of an object in such a machine takes place during the corresponding stopping time of the carriage and is therefore effected in a much more reliable manner. Likewise, it is during the other of these stops of the carriage that the object is released. I

In accordance with another aspect of the invention, the transfer device has a course which is tangential to the path followed by an object when it is driven by any one of the rotary devices associated with the printing station.

Thus, the engagement of an object by the rotary device associated to the second printing station, is made in accordance with a movement which continues that of the transfer device in such a way that the latter can return, that is, in the direction of the first printing station. as soon as the object has been seized by the rotary device associated with the second printing station without being obliged to wait until this rotary device has followed a course sufficient to free the said object from the transfer device. The result of this is that the time necessary for the return of the transfer device to the initial period is much shorter and the rate of the machine is substantially increased.

In accordance with a preferred embodiment of the invention, the transfer device comprises a receiving fork for an object supported at the end ofa lever forming one of the sides of a deformable parallelogram, the said lever being alternatively driven parallel to itself from a first position, where it is tangential to the course followed by an object on the rotary device associated with the first printing station, to a second position where it is tangential to the course which will be followed by the said object on the rotary device associated with the second printing station.

This particularly simple and robust embodiment is very efficacious and permits the rate of working of the machine rate to be increased by more than 50 percent.

LII

To ensure that. in the course oftransferring one object from one printing station to the other, the object is not ejected from the transfer device. this latter is. in accordance with another aspect of the invention. equipped with a suction nozzle disposed in the hollow of the reception fork and adapted to keep the object in place on the fork.

In accordance with another aspect ofthe invention. the base and the gripping tip of a rotary device associated with a printing station are each set on an independent pinion engaging with a particular toothed rack integral in translation with the associated screen. and the rack associated to the said tip is mounted longitudinally sliding and carries. at each of its ends. a roller cooperating with a flat integral with the screen and perpendicular to the direction of sliding ofthe said rack.

This device permits the gripping tip to be controlled by a rack different from the rack controlling the associated base. in spite of the vertical movement of the screens during their return to the initial position.

In accordance with another aspect of the invention, the presentation of the objects to be printed at the first printing station is ensured by a transfer chain advancing step by step. controlled synchronously with the carriage which carries the screen, while after printing their second surfaces, the objects are deposited by the rotary device associated with the second printing station on a drying chain advancing continuously. separate from the said transfer chain.

This arrangement allows the machine to be fed at a rate corresponding to the high rate of working this machine, and furthermore permits the continuous direct passing of the objects which havejust been printed. into a drying oven disposed upstream from the printing machine.

An embodiment of the invention will now be described by a way ofexample, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is an elevation of a machine embodying the invention, with parts cut away,

FIG. 2 is a plan view with parts cut away and with some parts omittedand FIG. 3 is a lateral view in the direction of the arrow III of Fig. 2, again with some parts omitted.

FIG. 4 is a close up view of the transfer mechanism of the present invention.

In the embodiment shown in the drawings, the invention is applied to a printing machine of the type described in the above mentioned U.S. patent: the various elements of this machine will only be described briefly below.

Two parallel supporting end plates 2 and 3, having the configuration of chairs, supported by a stand 1, are joined by two vertically superposed horizontal cylindrical bars 4 and 5.

On the ends of the upper horizontal bar 4 are pivoted arms 6 and 6' joined by a cylindrical bar 8. In a similar manner on the ends of the lower horizontal bar 5 are pivoted two arms 7 and 7' respectively superposed to the arms 6 and 6, and joined by a cylindrical bar 9, vertically superposed to the bar 8.

On the bars 8 and 9 slides longitudinally a carriage C formed of two vertical arms 10 and 11 slidingly engaged on the bars 8 and 9 and joined by a horizontal bar 12. As is best seen in FIG. 2, the bar 12 carries two overhung transverse supports 13 and 14 cross braced by bars 15 and 16 and intended to carry silk screens 17 and 18 forming the principal elements of the two printing stations of the machine. The horizontal bar 12 carries on its side opposite the supports 13 and 14, a yoke 19 in which is engaged an arm 20 integral with a fork 21 articulated on a carriage 22 mounted to be longitudinally movable on the horizontal bar 5. The carriage 22 furthermore carries a roller 23 which rolls in a guide 24 made in the stand 1 as shown in FIG. 3. Such an arrangement is also shown in the above-cited U.S. patent particularly in FIG. 2 thereof.

In accordance with the present invention, the movement of the carriage 22 is controlled, by means of a flat cam 35, such as a vertical disc, driven in rotation by a control shaft 36 carrying a pinion 37 around which passes a chain 38 driven by a pinion 39. The pinion 39 is mounted on the output shaft 40 of a speed reducer 46 whose input shaft 41 is driven by a motor 42 by means of pulleys 43 and 44 and a transmission belt 45. The carriage 22 supports a vertical flat iron 122 on which is articulated a link 25 itself articulated at its other end on a lever 26 pivotably mounted at 27 on the frame. The lever 26 has a slot 28 in which is movably engaged a roller or finger 29 supported by a horizontal bar 30 slidably mounted, as shown in Fig. 2, at 31 and 32 in sleeves respectively integral with the plates 2 and 3 of the frame. The bar 30 also carries two rollers 33 and 34 held in contact with the camming surface of the cam 35 in positions diametrically opposite one another, as shown in Figs. 1 and 2.

in the following, the corresponding, and identical, respective elements of the two printing stations of the machine are given the same reference numerals and are distinguished one from the other by the use of a prime.

The carriage 22 supports a toothed rack 47 which engages with two pinions 48 and 48' established at a distance one from the other; the radii of the pinions are equal to the radii of curvature of those surfaces of the oval objects to be printed. The pinions 48 and 48' are set on shafts 49 and 49 respectively, at the other ends of which are set support bases 50 and 50 respectively associated with the two printing stations of the machine. In a manner known per se the rotary devices associated with these printing stations are completed by gripping tips 51 and 51' carried at the end of arms 76 and 76' set on shafts 77 and 77 which are arranged in axial alignment with the shafts 49, respectively and 49. The shafts 77 and 77' are mounted to be longitudinally slidable in fixed supports under the control of levers 52 and 52' respectively actuated by pneumatic jacks 53 and 53'. Furthermore, the shafts 77 and 77' are respectively integral in rotation with the pinions 78 and 78' which engage with a toothed rack 79.

The levers 52 and 52' are mounted to pivot at a fixed point and each lever carrier a stop capable of actuating a respective microswitch MS and MS.

in accordance with the present invention, the rack 79 is mounted to be longitudinally slidable in stationary sleeves 80 and 80', carried by the machine frame, and carries, at its ends, rollers 81 and 81' which bear against respective ones of the flat vertical plates 82 and 82 each integral with a respective one of the supports 13 and 14 carried by the bar 12 of the carriage C.

The scrapers, or squeegees, 62 and 62' respectively associated with the two printing stations of the machine are mounted on arms 63 and 63 integral with two horizontal bars 66 and 65' themselves fixed on a vertical arm 67. The arm 67 pivots at 68 on a bar 70 supported by a hub 71 rotatably mounted on the bar 4. The arm 67 also pivots at 69 on an arm 72 which pivots on its other end on the horizontal bar 9. Thus,

as is described in the US. patent mentioned above,on the end of the arm 6' elongated for this purpose is articulated a bar 88 of adjustable length, at the other end 87 of which is articulated a lever 85. The articulated lever 85 has a fixed pivot point 86 a carrier roller 84 which cooperates with a cam 83 set in rotation on the driving shaft 36 previously mentioned.

In accordance with the invention, the arms 63 and 63' which carry the scrapers 62 and 62 are mounted to be vertically displaceable under the control of pneumatic jacks 64 and 64' which are supported by projections of the machine frame and electrically connected to be activated by microswitches MS and MS.

The presentation at the first printing station of objects to be printed is ensured by a transfer conveyor belt formed by two parallel synchronous chains 54 and 54' carrying respectively supports 55 intended to receive the body of the object to be printed and supports 55' intended to receive the base of these objects. The chains 54 and 54 pass over a drive pinion 56 rotated by a chain 57 driven by a pinion 58. The pinion 58 receives its movement from a pinion 59 set on the shaft of a Maltese cross 60 which cooperates with a crank pin 61 set on the output shaft of the reducer 46.

Between the two printing stations of the machine, there is a transfer device which comprises a fork 90 fixed to the end of a lever 91 articulated at 92 and 93 respectively on two arms 95 and 96 set respectively on two rotative axes 97 and 98 in such a way that the lever 91 forms one ofthe sides ofa deformable parallelogram and is displaced only in translation, i.e. so that it maintains its vertical orientation. The axes 97 and 98 are integral with pinions joined by a chain 99; elsewhere a pinion 100 rigidly mounted on the axis 97 engages with a pinion 101 on which is articulated a link 102 itself articulated on a lever 103. The lever 103 which pivots about a fixed shaft 104 carries at its other end a roller 105 which cooperates with a hollow cam in a flat vertical disc 106.

The bottom of the fork 90 is furthermore supplied with a suction nozzle 120 connected to a suction device (not shown).

The machine is completed by a drying chain formed by parallel chains and 111 between which are disposed arms 107 mounted on pivots 108 and 109, respectively carried by the chains 110 and 111. The chains 110 and 11] pass over driving pinions 112 and 113 mounted on a shaft 114, controlled by a pinion 115, integral in rotation by means of a chain 116 and a pinion 117 on the output shaft 40 of the reducer 46. The chains 110 and 111 furthermore pass over pinions 118 and 119 arranged near the rotary device associated with the second printing station on the machine and then pass into a drying oven (not shown).

There will now be described the working cycle of the printing machine for printing the two surfaces of the same object. It will be supposed for this purpose, thatthe object supported by the supports 55 and 55' of the chain 54 and 54 hasjust been gripped by the rotary device 50 and 51 associated with the first printing station. This gripping takes place during the stopping of the carriage C carrying the screens at its furthest left-hand position of corresponding horizontal movement. The cam 35 is conformed in such a way that the carriage C carrying the screens has a determined stop period at each of its end positions in such a way that the gripping point 51 has time to grip the object to be printed with a great reliability.

The carriage carrying the screen C carries out its horizontal translation movement under the control of the carriage 22 itself set to work by the set of rods formed by the link 25, the lever 26, the sliding bar 30, the rollers 33 and 34, and the cam 35 at the same time, the rotary device 50 and 51 actuated by the rotation of the pinions 48 and 78 which engage respectively with the racks 47 and 79, apply the gripped objects against the screen 17 and make it roll, without sliding, in contact with the screen, which itself is horizontally displaced while the squeegee 62 applied against the screen 17 remains stationary and ensures the passage through the openings of this screen of the product necessary for the printing of the first surface of the object. When the printing is finished, that is to say when the carriage carrying the screen C arrives at its extreme righthand position the object with one surface printed, is placed by the rotary device 50 and 51 in the fork of the transfer device, which at this instant occupies a position tangential in relation to the course followed by the said object. Again, since the cam 35 is conformed so that the carriage C carrying the screens makes a determined stop period in each of its extreme positions of sliding, it is possible to retract the gripping tip 51 to withdraw it from, and free, the object with great functional reliability.

The object in course of being printed is now taken in charge by the transfer device and it is important to note that the movement of the latter is initially in a direction substantially tangential to the path followed by the object when it is held by the rotary device 50 and 51 in such a way that the transfer device can immediately enter in action without waiting for a previous withdrawal of the rotary device 50 and 51. Furthermore, the suction nozzle 120 ensures a secure maintenance of the object in the fork 90 during the transfer of the object from the first to the second printing stations.

Durning the transfer, the following operations are effected in synchronism: the presentation of a new object directly above or below the first printing station by advancement of a step of the chains 54 and 54 under the control of the Maltese cross 60; vertical disengagement of screens 17 and 18 and of the scrapers 62 and 62' resulting from the deformation of the deformable parallelograms 6, l0, 7 and 6', l1, 7' under the action of the set of rods comprising successively the cam 83, the roller 84, the lever 85, the bar 88 and the extension of the arm 6'; and finally return of the carriage C carrying the screens to its initial position as a result of a new movement of the set of rods and the operation ofcam 35. Thus. as will be understood, in a manner known per se the vertical upward movement of scrapers 62 and 62' is greater than that of the screen 17 and 18 due to the fact that parallelogram 70, 67, 72 which carries the scrapers 62 and 62' has a lever arm defined by bar 70, longer than that of the deformable parallelogram described above, which carries the screen 17 and 18. Thus, as is known, this vertical raising of scrapers 62 and 62, with respect to the screens 13 and 14 during the return of the latter into the initial position is necessary to avoid forcing the printing product through the openings of the screens during this movement.

in a similar manner to that which has been described above, the final phase of the movement of the transfer arm 91 to the right is tangential to the movement of the rotary device 50 and 51' associated with the second printing station. As a result, the rotary device can immediately take over the control of the object being printed, this takeover occurring during the preset stop period of the carriage C at its extreme left-hand position of its horizontal displacement. This interposition is made in a manner known per se by advance of the tip 51 in the direction of the base 50 under the control of the lever 52' operated by thejack 53'.

The tangential movement of the lever 91 permits it to withdraw immediately, by continuing its circular movement so as to move downwardly and to the left, as soon as the object has been taken in charge by the rotary device 50' and 51' without waiting for this device to have started its rotation; from this results a reduction in the time necessary for the return of the transfer device to its initial position, the extreme left-hand point of its circular travel path, and as a consequence a substantial improvement in the rate of operation of the machine.

As will be understood, the printing of the second surface of the object is made in a similar manner to the printing of the first surface and during the printing of this second surface at the second printing station, the first face of a new object is printed at the first printing station.

The object whose two surfaces have just been printed is deposited by the rotary device 50 and 51 associated with the second printing station in one of the balancing arms 107 of the drying chain 110 and Ill and is led into the associated drying oven.

The rack 79 which engages with the driving pinions 78 and 78 of the gripping tips 51 and 51' is brought back into the initial position by the carriage carrying the screen C, during the return movement of the latter. As has been seen, the rollers 81, 81' carried by the said ratchet cooperate for this purpose with vertical plates 82, 82 integral with the carriage for carrying the screen C.

If, during the advanced movement of any of the gripping tips 51, 51, there is not an object to seize the corresponding lever 52, 52' closes the associated microswitch MS, MS, and this actuates the corresponding jack 64, 64 in such a way that the associated squeegee 62, 62' is raised from the corresponding screen and there is therefore no drive of the printing product through the screen during the movement of the carriage carrying the screen C.

lclaim:

1. In a machine for printing, in a single pass, two surfaces of an object having an oval transverse section, comprising:

a. a first printing station including:

i. a first printing means; and

ii. a first rotary means in register with said first printing means and arranged to grip an object and carry it in a circular path to roll without sliding in contact with said first printing means;

b. a second printing station including:

i. a second printing means; and

ii. a second rotary means in register with said second printing means and arranged to grip an object and carry it in a circular path to roll without sliding in contact with said second printing means;

c. a transfer means disposed between said first and second printing stations and composed of a transfer lever, a fork carried at the end of, and rigidly connected to, said lever for receiving an object and for transferring such object from one printing station to the other, and a suction noz zle disposed in the hollow of said fork;

d. means for displacing said transfer means from a first position where it receives an object carried by said first rotary means after printing of one surface of the object, to a second position where it places said object in said second rotary means for printing of the other surface of the ob ject, said means for displacing being composed of two parallel arms articulated on said lever at two distinct pivots, and two axes spaced vertically from one another at a distance equal to that of said pivots, each said arm being mounted on a respective one of said axes for rotation therewith, the improvement wherein;

said arms, said lever and said axes constitute a mechanical deformable parallelogram linkage for moving said transfer means only in translation along a circular path;

fv said machine further comprises synchronizing means connected between said rotary means and said axes for rotat ing said axes unidirectionally in synchronism with said rotary means in a manner such that said transfer means are driven in translation in only one direction along a circular path between said first position where its path is tangential to the course followed by an object on said first rotary means and said second position where its path is tangential to the course to be followed by such object on said second rotary means;

g. said axes are positioned so that said first and second positions of said transfer means are at respectively opposite sides of the vertical plane passing through both of said axes; and

h. said means for displacing said transfer means are arranged for moving said transfer means in one direction along a circular path tangential to the paths imparted to objects by both of said rotary means, the circular path followed by said transfer means having an upper half along which said transfer means moves in a direction from said first station to said second station and a lower half along which said transfer means moves back from said second station to said first station.

2. A machine as defined in claim 1 further comprising:

control means for imparting alternating horizontal displacements to said carriage;

a transfer chain connected for controlling the delivery of objects to said first printing station;

first drive means connected to advance said transfer chain in a step-by-step manner in synchronism with the alternating displacements of said carriage;

a drying chain distinct from said transfer chain and positioned for receiving objects from said second printing station after such objects have been printed therein; and

second drive means connected to impart a continuous movement to said drying chain.

3. In a machine for printing, in a single pass, two surfaces of an object having an oval transverse section, comprising:

a. a first printing station including:

i. a first printing means; and

ii. a first rotary means in register with said first printing means and arranged to grip an object and carry it in a circular path to roll without sliding in contact with said first printing means;

b. a second printing station including:

i. a second printing means; and iiv a second rotary means in register with said second printing means and arranged to grip an object and carry with said second printing means;

printing stations and composed of a transfer lever and a fork carried at the end of said lever for receiving an object;

. means for displacing said transfer means from a first position where it receives an object carried by said first rotary means after printing of one surface of the object, to a second position where it places the object in said second rotary means for printing the other surface of the object, said means for displacing being composed of two parallel arms articulated on said lever at two distinct points, and two axes spaced vertically from one another at a distance equal to that of said pivots, each said arm being mounted on a respective one of said axes for rotation therewith, the improvement wherein;

. said means for displacing said transfer means moves said transfer means in a course tangential to the circular path followed by an object in at least one of said rotary means; said arms are set on said axes and said axes are controlled to pivot in synchronism with said rotary means associated with said printing stations in such a way that said transfer lever forms one of the sides of a deformable parallelogram and is driven only in translation between said first position where it moves tangentially to the course followed by an object on said first rotary means and said second position where it moves tangentially to the course which will be followed by the object on said second rotary means; and said two axes of said transfer means are integral in rotation with a common pinion and, for control of the pinion, said transfer means comprises a cam mounted for rotation in synchronism with said rotary means. a control lever articulated at a fixed point, a roller carried at the end of said control lever and held in contact with said cam, and a joining link articulated to said control lever and to said pinion.

4. In a machine for printing, in a single pass, according to the open silk screen process, two surfaces of an object having an oval transverse section, comprising:

a movable carriage;

b. a first printing station including:

i. a first printing means; and

ii. a first rotary means in register with said first printing means and arranged to grip an object and carry it in a circular path to roll without sliding in contact with said first printing means;

. a second printing station including:

i. a second printing means; and

ii. a second rotary means in register with said second printing means and arranged to grip an object and carry it in a circular path to roll without sliding in contact with said second printing means;

. each said printing means comprising a silk screen and a scraper carried by said carriage and movable vertically with respect thereto, and each said rotary means comprising a base and a gripping tip movable in the direction of said base for applying an object to be printed against said base;

. at least one rack movable horizontally together with said screens of both of said printing means and connected to drive said base and said tip of each said rotary means in synchronous rotation;

transfer means disposed between said first and second printing stations for transferring such object from one printing station to the other; wherein;

. means for displacing said transfer means from a first posisaidmeans for displacing said transfer means moves said transfer means in a course tangential to the circular path followed by an object in at least one of said rotary means; and

. said machine further comprising control means for imparting alternating horizontal displacements to said carriage, said control means including: a rotatable cam having a profile which ensures a determined stop period for said carriage at each of the extreme ends of its horizontal displacement; a bar mounted to be longitudinally slidable; two rollers carried by said bar to contact said cam at positions diametrically opposite each other; a lug supported by said bar. and constituting a pivot; a lever pivotally mounted at a fixed point and provided with a slot in which said pivot is engaged; and an articulated link connected between said lever and said carriage.

ln a machine for printing, in a single pass, according to the open silk screen process, two surfaces of an object having an oval transverse section, comprising:

a movable carriage;

a first printing station including:

i. a first printing means; and

ii. a first rotary means in register with said first printing means and arranged to grip an object and carry it in a circular path to roll without sliding in contact with said first printing means;

a second printing station including;

i. a second printing means; and

ii. a second rotary means in register with said second printing means and arranged to grip an object and carry it in a circular path to roll without sliding in contact with said second printing means;

. each said printing means comprising a silk screen and a scraper carried by said carriage and movable vertically with respect thereto, and each said rotary means comprising a base and a gripping tip movable in the direction of said base for applying an object to be printed against said base;

transfer means disposed between said first and second printing stations for transferring such object from one printing station to the other;

means for displacing said transfer means from a first position, where it receives an object carried by said first rotary means after printing of one surface of the object, to a second position, where it places said object in said second rotary means for printing of the other surface of the object, the improvement wherein:

. said means for displacing said transfer means moves said and said machine further comprises;

. control means for imparting alternating horizontal displacements to said carriage, said control means including: a rotatable cam having a profile which ensures a determined stop period for said carriage at each of the extreme ends of its horizontal displacement;

. two racks movable horizontally together with said screens of both of said printing means, one of said racks being connected to drive said bases of both of said rotary means and the other of said racks being connected to drive said tips of both of said rotary means in synchronism with said bases;

. means supporting said other of said racks for permitting it to slide only in a longitudinal horizontal direction;

. means defining two flat surfaces integral with said car riage and extending perpendicular to the direction of movement of said other of said racks, each said surface being adjacent a respective end of said other of said racks;

. two rollers each mounted on a respective end of said other of said racks and engaging a respective one of said surfaces; and

m. whereby said surfaces bear against said rollers even if said carriage is moved into a raised position.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,533,353 Dated er 1 h, 1970 lnventol-(s) Louis Gilbert Dubuit It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading of the patent, line 2, change "Vetrune" to -Vitruve. Column 3, line 29, change ",respectively and 49' to -and 49 respectively. Column 5, line 26, change "its" to -the. Column 7 line 65, change wherein; to -,and-.

EQQNED mi SEAUED at; a. 1971 WILLIAM R. JR- mung 0mm Gomissionar 0? Palm USCOMM-DC 6031 6-909 FORM PO-1050 (10-69) u s, GDVCINMENT rum-mu: ornc: "n o-ssi-su 

